Results have been obtained indicating that 13-cis retinoic acid is capable of potentiating the production of a secondary IgE antibody response without a demonstrable primary response. Work during the coming year will focus on the mechanism of the potentiation of the secondary response as well as the suppression of the primary response. This will be begun by more completely defining the scope of this effect; that is, which antibody classes are effected, etc., and then investigating the actual cellular or soluble elements affecting these phenomena.